I attended some programming classes but I barely remember anything...I am starting a project which is a big countdown that consists of 25 7segments leds.It goes from 9999999999999999999999999 to 0. So it would take billions of years to end...I do not know if is necessary to write code or I just need a diagram.

It should work without a pc connected to it.

What materials will I need? As you can imagine any help would be greatly appreciated

It is an art project so visual aspect is quite important. I was thinking in using quite big digits (3-4 inch). I do not know if this has a mayor impact on the structure of the electronic device.Everything that makes things easier is welcome So if it is better I would go for the 32 digits.As I mentioned before I am completely new to all this so I appreciate your patience and any advice to keep it as simple as possible.I found this one: http://www.ebay.es/itm/Protoboard-700-contactos-Breadboard-placa-prototipos-soldadura-Arduino-/170927079955?pt=LH_DefaultDomain_186&hash=item27cc0c4213#ht_2473wt_1190 , is this big enough?

The digit changes every second. That is why it will take so long.

I already know how to make a simple 1 digit countdown, but I can not find the way to make the 25 digits one… any help with diagrams or code is more than welcome

This kind of 4" digit?http://www.kingbrightusa.com/category.asp?catalog%5Fname=LED&category%5Fname=KC1%2DDigit+4%2E0in&Page=1

I'd recommend the Common Anode parts, drive from 12V, connect the cathode segments to TPIC6B595 shift registers to drive them.

This board here can drive 12 digits, use 2 boards and wire up one TPIC6B595 for the 25th digit.Probably want to wire the anodes together seperately and not source from the board tho. Connect grounds together.I sell bare boards for $5 each mailed to US locations, all thru hole, easy to assemble. International, a little more for postage.Complete kit, or assembled tested boards, I'd have to price up.

The actual counting down part is easy.set up 25 bytes with 9 in each.once a time period, test if the lowest digit is not 0 and decrement it.If it is 0, set it to 9 and decrement the next digit. if the next one is not 0, decrement it. if it is 0, set it 9 and decrement the next digit.Will have one big long chain checking if a digit is to rollover or not.Longest chain will from 1000000000000000000000000 to 0999999999999999999999999And you can add leading 0 blanking too.